Wireless telemetry auto for torque measurement system

ABSTRACT

A torque measurement system that includes a rotor device and a stator device can perform automatic tuning to improve the initial tuning performed during design and assembly. The stator device can include a variable capacitive element and a micro-controller configured to adjust a capacitance value of the variable capacitive element. Additionally or alternatively, the rotor device can include a variable capacitive element and a micro-controller configured to adjust a capacitance value of the variable capacitive element. The adjustment of the capacitive elements can be based on the quality of signal detected at either the rotor device or stator device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and is a continuation of U.S.patent application Ser. No. 13/155,937, entitled “Wireless TelemetryAuto Tuning for Torque Measurement System,” filed Jun. 8, 2011 by VishalMalhan. This application claims priority to the following application,the entire disclosure of which is incorporated herein by reference:

-   Ser. No. 13/155,937 Wireless Telemetry Auto Tuning for Torque    Measurement System Jun. 8, 2001

TECHNICAL FIELD

This disclosure relates generally to torque measurement systems and,more specifically, to techniques for tuning a telemetry system of atorque measurement system.

BACKGROUND

A torque measurement system typically includes a rotor device (rotor)and a stator device (stator). The rotor is generally configured toattach to a rotating system such as an engine turbine, gearbox,transmission, or other piece of rotating equipment. The rotor includesstrain gages for sensing torque, rotor electronics (RTE) for performingsignal processing operations, and an antenna for inductively receivingpower from the stator and for communicating with the stator. The statoris typically stationary and external to the rotating system and includesa coupling module in close proximity to the antenna of the rotor forreceiving a signal from the RTE. The coupling module is often times inthe shape of a caliper and referred to as a caliper coupling module(CCM). The CCM transfers the signal received from the rotor to statorelectronics (STE) that perform signal processing to extract the torquemeasurements in the signal. The stator may, for example, work inconjunction with a personal computer to process and present the datacollected by the RTE. The stator can also transmit instructions to theRTE, provide power to the RTE through inductive coupling, and receivestatus information transmitted by the RTE.

The rotor and stator each include an inductive antenna forbi-directional communication. Initially, the antennas are manually tunedat the factory where the torque measurement system is assembled. Thistuning ensures that the rotor receives an adequate signal from thestator, and vice versa. This initial tuning generally matches theresonant frequency of the RTE and the STE close to the telemetryfrequency through the selection of electronic components, such ascapacitors. Manufacturing variations in electronic components, ageing ofelectronic components, as wells as variations in operating conditions,and other variable factors, however, can cause the tuning of theantennas determined during the initial tuning to no longer be accurateonce a system is assembled and installed at a customer location. Afterassembly, however, the rotor antenna and stator antenna are typicallynot easily tunable.

SUMMARY

This disclosure generally describes a torque measurement system thatincludes a rotor device and a stator device. The rotor is generallyconfigured to attach to a rotating system such as an engine turbine,gearbox, transmission, or other piece of rotating equipment. The statoris typically stationary and external to the rotating system and includesa coupling module in close proximity to an antenna of the rotor. Therotor and stator each include an inductive antenna for bi-directionalcommunication. According to techniques of this disclosure, an inductiveantenna of the rotor, stator, or both can be automatically tuned in amanner that may improve both power transfer and data transfer betweenthe rotor and stator.

In one example, a torque measurement system includes a stator deviceconfigured to receive a signal from a rotor device. The stator deviceincludes a first variable capacitive element and a firstmicro-controller configured to adjust a first capacitance value of thefirst variable capacitive element. In another example, a torquemeasurement system includes a rotor device configured to transmit asignal to a stator device, and the rotor device includes a variablecapacitive element and a micro-controller configured to adjust acapacitance value of the variable capacitive element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram that illustrates one example of a torquemeasurement system configured to implement aspects of this disclosure.

FIGS. 2A-2D are graphs showing the frequency response of variousportions of the system described in this disclosure.

FIG. 3 is a circuit diagram showing components of rotor electronicsimplementing aspects of the present disclosure.

FIG. 4 is a circuit diagram showing components of stator electronicsimplementing aspects of the present disclosure.

FIG. 5 is a circuit diagram of a variable capacitive componentimplementing aspects of the present disclosure.

FIG. 6A is a flow diagram illustrating a stator tuning techniqueconsistent with the present disclosure.

FIG. 6B is a flow diagram illustrating a rotor tuning techniqueconsistent with the present disclosure.

DETAILED DESCRIPTION

This disclosure generally describes a torque measurement system thatincludes a rotor device and a stator device. The rotor is generallyconfigured to attach to a rotating system such as an engine turbine,gearbox, transmission, or other piece of rotating equipment. The statordevice is typically stationary and external to the rotating system andincludes a coupling module in close proximity to an antenna of therotor. The rotor and stator each include an inductive antenna forbi-directional communication. According to techniques of thisdisclosure, an inductive antenna of the rotor, stator, or both can beautomatically tuned in a manner that may improve both power transfer anddata transfer between the rotor and stator.

In this disclosure, “stator tuning” generally refers to adjustingparameters, such as a capacitance value, of stator components to adjustthe overall tuning of a torque measurement. Similarly, “rotor tuning”generally refers to adjusting parameters, such as a capacitance value,of rotor components to adjust the overall tuning of a torque measurementsystem. “System tuning” or “overall tuning,” as used in this disclosurecan refer to any of stator tuning, rotor tuning, or a combination ofboth.

FIG. 1 is a block diagram that illustrates one example of a torquemeasurement system 100 configured to implement aspects of thisdisclosure. Torque measurement system 100 includes rotor 110 and stator120. Rotor 110 includes flange 111, holes 112 a-112 d, ring 113, antenna114, and circuitry 115. Antenna 114 and circuitry 115 may collectivelybe referred to as the rotor electronics (RTE). Stator 120 includescoupling module (CM) 121, antenna 122, signal processing module (SPM)123, and computer 124. Rotor 110 connects to a rotating mechanism suchas a turbine of an engine through holes 112 a-112 d in flange 111.Flange 111 contains a series of strain gages (not shown) for makingtorque measurements as rotor 110 rotates. The output of the straingauges, also referred to as torque measurement signals, is transmittedfrom the strain gauges on flange 111 to circuitry 115. Circuitry 115 maybe embedded on a printed circuit board and configured to perform aseries of signal processing operations, such as amplification,digitization, and/or amplitude modulation, on the strain gage outputprior to transmitting the torque measurement signals to stator 120 viaantenna 114, which may be embedded in ring 113.

Antenna 114 may be configured to both transmit and receive a radiofrequency (RF) signal to and from antenna 122 of stator 120. The RFsignal can be amplitude modulated to include digital data for purposesof communication. In addition to digital communication data, stator 120also wirelessly supplies power to rotor 110 via electromagneticinduction from antenna 122 to antenna 114. When supplying power but nottransmitting data, the RF signal transmitted from stator 120 to 110 maynot be amplitude modulated. The transmissions between antenna 114 andantenna 122 occur at a selected carrier frequency, which is often eitherapproximately 6.78 MHz or 13.56 MHz but may also be at otherfrequencies. The carrier frequency is also sometimes referred to as thetelemetry frequency. When torque measurement system 100 is in operation,ring 113 is typically placed less than a few centimeters away from CM121 and antenna 122. In some implementations CM 121 can be a calipercoupling module in the shape of a caliper that partially surrounds ring113.

Stator 120 receives the signal with the torque measurement data viaantenna 122 from antenna 114 through inductive communication. Antenna122 and antenna 114 can be inductively coupled coils, hoop antennas, orother appropriately suited types of antennas. Antenna 122 may beincluded in CM 121 which is located in close proximity to antenna 114 ofrotor 110. CM 121 and SPM 123 perform various signal processingoperations, such as demodulation and amplification, on the receivedsignal to extract the torque measurement data obtained by rotor 110. CM121, antenna 122, and SPM 123 may collectively be referred to in thisdisclosure as stator electronics (STE). Computer 124 can present thetorque measurement data to a user of the system of FIG. 1.

The system of FIG. 1 is intended to illustrate the functionality ofrotor 110 and stator 120 by showing one example configuration. Thevarious functional units described for FIG. 1, however, may beimplemented in numerous other configurations. For example, in someimplementations the functionality of SPM 123 and computer 124 may becombined into a common device or unit. As another example, in someimplementations antenna 122, CM 121, and SPM 123 may be included in acommon device or unit, but in other examples, CM121 and SPM 123 may beseparate devices or units communicatively coupled through a wired orwireless channel.

The RTE and STE can initially be tuned when rotor 110 and stator 120 areassembled. As will be described in more detail below, the STE includes aseries LC tuned circuit that includes a capacitor (C) in series with aninductor (L). The current in antenna 122 may be at a maximum value orclose to a maximum value when the resonant frequency of the series LCcircuit is approximately equal to the telemetry frequency, i.e. thecarrier frequency. Additionally, as will be described in more detailbelow, the RTE includes a parallel LC tuned circuit, which includes acapacitor (C) in parallel with an inductor (L). The current in antenna114 may be at a maximum value or close to maximum value when theresonant frequency of the parallel LC circuit of the RTE isapproximately equal to the telemetry frequency. The initial tuning atthe time of assembly includes determining a C value for the STE and a Cvalue for the RTE, respectively.

The tuning performed at the time of assembly, however, may no longer beaccurate when the system is installed, at a customer location forexample. This is often true because the environments in which torquemeasurement systems are used tend to have a lot of metal in closeproximity to antenna 122 and antenna 114, which can alter the optimaltuning Additionally, when initially tuning antenna 122 and antenna 114,it can be difficult to account for manufacturing variations that canoccur with various components, as well as the changes that can occur tocomponents as the components age and wear. As will be described in moredetail below, in accordance with techniques of this disclosure, one orboth of antenna 114 and antenna 122 can be automatically tunable, thusallowing for the initial tuning done at the factory to be refined oncethe torque measurement system is installed. By tuning antennas 114and/or 122, the amount of power received by rotor 110 from stator 120may be increased, and the quality of data communication between rotor110 and stator 120 may be improved.

As will be described in more detail below, aspects of the presentdisclosure include the use of one or more microcontrollers in either orboth of rotor 110 and stator 120 to perform an automatic tuningprocedure. The automatic tuning procedure may, for example, be performedeach time the torque measurement system is powered on, periodically, orupon user command. The automatic tuning procedure may include statortuning, rotor tuning, or both. Rotor 110 and stator 120 might typicallybe coarsely tuned at the time of assembly, and the automatic tuningprocedure described in this disclosure may serve as a fine adjustment tothat coarse tuning. As will be described in more detail below, thetechniques of this disclosure may implement stator tuning by utilizing avariable capacitive element in the STE that can be controlled by amicrocontroller to adjust the C value in the LC circuit of the STE. Thetechniques of the present disclosure may additionally or alternativelyimplement rotor tuning by utilizing a variable capacitive element in theRTE that can be controlled by a microcontroller to adjust the C value inthe LC circuit of the RTE.

FIG. 2 a is a graph showing the frequency response of the rotor LCcircuit measured independently (curve 201), the stator LC circuitmeasured independently (curve 202), the frequency response of theoverall system (curve 203), and the telemetry frequency (line 204). Ascan be seen by the narrowness of curve 202 compared to curve 201, thatSTE has a higher degree of selectivity compared to the RTE. Accordingly,the 3 dB-bandwidth (i.e. the frequency at which output power drops byapproximately 50%) is approximately two MHz for the RTE but only a fewhundred KHz for the STE, making the overall system 3 dB bandwidthapproximately 1 MHz. The frequency response of the overall system is aproduct of both the rotor frequency response and the stator frequencyresponse, but due to the higher degree of selectively of the stator, insome instances, tuning the stator may have more effect on the overallsystem frequency response.

In some implementations, tuning may occur at only the RTE or only theSTE. In other implementations, tuning may occur at both the RTE and theSTE. In implementations where tuning occurs at the both the RTE and theSTE, the tuning may occur concurrently, or the system may first attemptto tune the STE and only tune the RTE if tuning the STE proves to beinsufficient, or vice versa.

FIGS. 2B-2D are graphs of system frequency response that show theinduced voltage in the RTE as a function of frequency response. Thetelemetry frequency is the frequency of the carrier that powers the RTE.The telemetry frequency is usually determined by a stable frequencysource such as a crystal oscillator in the stator electronics and doesnot typically change with either the stator or rotor electronics tuning.

FIGS. 2B-2D show a system response with three unique bands. FIG. 2Bshows the normal data band. Generally, it is desirable to tune thesystem such that the telemetry frequency is in the normal data band. Ifthe RF power input is adequate, the recovered voltage should also beadequate and the amplitude modulated digital signal should havesufficient modulation depth. FIG. 2C shows a forbidden band. In thisforbidden band shown in FIG. 2C, the voltage induced in the RTE ismaximum but an amplitude modulated digital signal does not havesufficient modulation depth for data transfer. FIG. 2D shows the datainversion band. This band generally operates the same as the normal databand, but digital data is inverted. For example, a digital signal of11010 in the normal band appears as 00101 in the data inversion band. Astator can be configured to detect inverted data, thus making the datainversion band also suitable for data communication. Tuning of thesystem, as described in this disclosure, generally includes adjustingparameters of the LC tuned circuits in a rotor and/or a stator such thatthe telemetry frequency is generally in the normal data band or datainversion band but not within the forbidden band.

One objective of stator tuning may be to adjust the gap between theresonant frequency of the stator LC and the telemetry frequency in orderto create sufficient power transfer from stator to rotor and reliabledata transfer from rotor to stator. Similarly, one objective of rotortuning is to adjust the gap between resonant frequency of the rotor LCand telemetry frequency to ensure sufficient power transfer from statorto rotor and reliable data transfer from rotor to stator.

FIG. 3 is a circuit diagram showing components of rotor electronics(RTE) 310 of a rotor device, such as rotor 110 of FIG. 1, that areconfigured to receive torque measurements signals from strain gages 330.RTE 310 includes antenna 314, fixed capacitor 316, variable capacitiveelement 317, signal conditioning module (SCM) 319, and micro-controller321. RTE 310 can both transmit a signal to a stator device and receive asignal from a stator device. When receiving a transmission, RTE 310receives an RF signal from a stator device at antenna 314. Thecomponents shown in box 318 comprise a parallel LC circuit. Fixedcapacitor 316 has a capacitance value selected during assembly of RTE310 to coarsely tune antenna 314 to the telemetry frequency in themanner described above with relation to FIGS. 2B-D. As will be describedin more detail below, micro-controller 321 can change the capacitivevalue of variable capacitive element 317 such that that the totalcapacitance of fixed capacitor 316 and variable capacitive element 317can be set to multiple different values. Micro-controller 321 can eitheridentify the value for variable capacitive element 317 that produces thebest tuning, or can transmit recorded data to a stator device so thestator device can identify the value for variable capacitive element 317that produces the best tuning

Identifying a desired tuning for the LC circuit of box 318 can beperformed by causing micro-controller 321 to record recovered voltagevalues (V_(RECOVERED)) for various values of variable capacitive element317. Based on the recorded values for V_(RECOVERED), micro-controller321 might set variable capacitive element 317 to a desired value.Alternatively, mircro-controller 321 may transmit the values ofV_(RECOVERED) to a stator device so the stator device can determine adesired value for variable capacitive element 317. A stator device, suchas stator 120 which includes computer 124 for example, may have greatercomputational resources than RTE 310, and thus can use moresophisticated techniques for determining a desired tuning than would bepractical to implement in RTE 310.

Determination of a desired value for variable capacitive element 317 mayinclude testing a group of values and identifying a preferred value fromthe group. Determination of a desired value may also include testingvalues for capacitive element 317 until an adequate value is foundinstead of testing an entire group of values. Additionally, as will beexplained in more detail below, the stator device may use the recordedvalues of V_(RECOVERED) for performing stator tuning. In someimplementations the tuning of RTE 310 may be based only on recordedvalues for V_(RECOVERED), but in other implementations V_(RECOVERED) maybe one of multiple variables that are monitored for the purposes ofdetermining a desired tuning.

As will be described in more detail below, RTE 310 may be configured tooperate in a tuning mode, where micro-controller can cause RTE 310 totransmit a signature byte that contains a series of bits known to astator. Upon receiving a confirmation of tuning from the stator device,RTE 310 can enter into a normal operating mode. If, however, RTE 310does not receive a confirmation of tuning within a certain period oftime, then micro-controller 321 can adjust the capacitance of variablecapacitive element 317.

In implementation, the functionality of SCM 319 may performamplification, filtering, signal rectification, analog-to-digitalconversion, low drop out regulation, amplitude shift keying, andnumerous other signal processing operations necessary or desirable forpurposes of measuring torque values and communicating with a statordevice. In some implementations, these various functions may beperformed by a plurality of units at various locations throughout RTE310. It should also be noted that the location of variable capacitiveelement 317 shown in FIG. 3 is merely one example configuration. In someconfigurations, for example, circuitry corresponding to the variousfunctionality of SCM 319, such as signal rectification, may occurbetween fixed capacitor 316 and variable capacitive element 317. Thecircuit diagram of FIG. 3 is merely intended to be one non-limitingexample of the electronics that might be found in a rotor device.

FIG. 4 is a circuit diagram showing components of stator electronics(STE) 420 of a stator device, such as stator 120 of FIG. 1. STE 420includes an RF generator and filter 421, stator antenna 422, fixedcapacitor 423, and variable capacitive element 424. The components shownin box 425 collectively form a series LC circuit. STE 420 furtherincludes signal processing module (SPM) 426, peak detector 427, peakcomparator 428, data inversion detection module 429, andmicro-controller 430. Although not shown in FIG. 4, STE 420 may alsoinclude circuitry for detecting data inversion as described in FIG. 2Dand may include amplitude modulation circuitry for modulating a signalwith data for purposes of communicating with a rotor device. STE 420 isconfigured to both transmit and receive a signal via stator antenna 422.

To transmit a signal, micro-controller 430 may cause RF generator andfilter 421 to generate an amplitude modulated signal for transmission toa rotor device. When receiving a signal SPM 426 can demodulate, filter,differentiate, and amplify the received signal. STE 420 may perform awide array of signal processing functions on both transmitted andreceived signals. For ease of explanation, this disclosure generallyascribes these various functions to SPM 426, but in someimplementations, these various functions may be performed by a pluralityof units at various locations throughout STE 420. The circuit diagram ofFIG. 4 is merely intended to be one non-limiting example of theelectronics that may be found in a stator device.

During tuning, SPM 426 can be configured to identify a signal from arotor device by identifying a signature byte transmitted by the rotordevice. After SPM 426 identifies a signal from a rotor, peak detector427 can detect the peak output of SPM 426, which is one measure of thequality of the received signal. Based on the peak value detected by peakdetector 427, micro-controller 430 may either adjust the capacitance ofvariable capacitive element 424 or determine that the system isadequately tuned and enter into a normal mode of operation. In someimplementations, peak comparator 428 may compare detected peaks for aset of capacitance values for variable capacitive clement 424, andmicro-controller can set variable capacitive element 424 to thecapacitance that results in the best signal quality, which in thisexample might be the capacitance that results in the largest detectedpeak value by peak detector 427.

In some implementations, either instead of or in addition to detecting apeak of a signal received at STE 420, micro-controller 430 may alsoreceive, from a rotor device, data identifying a recovered voltage atthe rotor device. Based on the recovered voltages at the rotor device,micro-controller 430 may either adjust the capacitance of variablecapacitive element 424 or determine that the system is adequately tunedand enter into a normal mode of operation. In some implementations, STE420 may compare recovered voltages for a set of capacitance values forvariable capacitive element 424, and micro-controller can set variablecapacitive element 424 to the capacitance that results in the bestrecovered voltage at the rotor device.

FIG. 5 shows an example of a variable capacitive component 501, whichcould be used in either a RTE or STE according to the techniques of thisdisclosure. Variable capacitive component 501 is configured to be ableto produce variable capacitances between lead 505 and lead 506. Variablecapacitive component 501 may, for example, be included in the variablecapacitive element 317 of FIG. 3 or variable capacitive element 424 ofFIG. 4. Variable capacitive component 501 includes 5 capacitors(capacitors 510 a-510 e) connected to one another in parallel. In otherconfigurations, different numbers of capacitors as well as capacitorsconnected in series may be utilized. Each of capacitors 510 a-510 e isconnected to lead 506 through a switch (switches 520 a-520 c). Whenswitch 520 a is closed, capacitor 510 a contributes to the capacitancebetween leads 505 and 506. When switch 520 a is open, capacitor 510 adoes not contribute to the capacitance between leads 505 and 506.Capacitors 510 b-510 e and switches 520 b-520 e contribute in a similarmanner.

Switches 520 a-520 e are configured to be controllable by amicro-controller, such as micro-controller 321 of FIG. 3 ormicro-controller 430 of FIG. 4. Switches 520 a-e may comprise digitallycontrolled switches that enable bi-directional current flow such astransistor-based switches (e.g. MOSFETs), or may be alternate types ofswitches such as electro-mechanical relays or PIN diode switches.

In one example, variable tuning of approximately +/−45 pF can beachieved by a configuration that uses 10 pF capacitors for capacitors510 a and 510 b, a 15 pF capacitor for capacitor 510 c, a 30 pFcapacitor for capacitor 510 d, and a 47 pF capacitor for capacitor 510e. Capacitors in parallel are added to determine a total capacitance.For example, using the example capacitance values given above, if all ofswitches 520 a-520 e are open, then the total capacitance of variablecapacitive element 501 is 0 pF. If only switch, 520 a is closed, thenthe total capacitance of variable capacitive element 501 is 10 pF. Ifonly switch 520 e is closed then the total capacitance of variablecapacitive element 501 is 47 pF. If all of switches 520 a-520 e areclosed, then the total capacitance of variable capacitive element 501 isthe sum of the capacitances of capacitors 510 a-510 e (112 pF in thisinstance). By closing different combinations of switches 520 a-520 e,the value of capacitive component 501 can be set to various valuesbetween 0 pF and 112 pF. Adding this additional capacitance to a fixedcapacitor in either an RTE or STE can change the total capacitance ofthe system, and hence adjust the tuning of the RTE or STE.

As described above in reference to FIG. 2A, STEs typically have a higherdegree of selectivity compared to RTEs. Accordingly, in an STE, it maybe desirable to utilize a variable capacitive element that increments insmaller values than a variable capacitive element used in an RTE. Insome implementations, a variable capacitive element like that of FIG. 5may use capacitors with greater capacitance, such as 20-30 pF, ifvariable capacitive component 501 is going to be implemented in a rotordevice, and use capacitors with less capacitance, such as 5-10 pF, ifvariable capacitive component 501 is going to be implemented in a statordevice.

FIG. 6A is a flow diagram illustrating a stator tuning techniqueconsistent with the present disclosure. FIG. 6B is a flow diagramillustrating a rotor tuning technique consistent with the presentdisclosure. As will be described in more detail below, the methods orportions of the methods described in relation to FIGS. 6A and 6B can beperformed either independently or concurrently. The methods of FIGS. 6Aand 6B will be described with reference to FIGS. 1, 3, 4, and 5. Tobegin stator tuning as shown in FIG. 6A, a user of a torque measurement,such as torque measurement system 100 of FIG. 1 powers on a statordevice, such as stator device 120 with STE 420 (601). STE 420, eitherautomatically or upon user command, enters into a tuning mode. STE 420,which inductively powers a rotor device, such as rotor device 110 withRTE 310, causes the rotor device to be powered on as part of enteringthe tuning mode.

When initially powered on, micro-controller 321 of RTE 310 beginsperiodically transmitting via the LC circuit of box 318 a signature byteto STE 420. The signature byte can be a series of bits identifiable bySTE 420. The stator device receives a signal from rotor device 310 atthe LC circuitry of box 425 (602) and attempts to identify thissignature byte within the received signal received (603). Signalprocessing module 426 can process the received signal to determine ifthe signature byte can be identified (603). If the signature byte cannotbe identified within the received signal (603, no), thenmicro-controller 430 can adjust the capacitance of variable capacitiveelement 424 (604). After changing the capacitance of variable capacitiveelement 424, STE 420 can continue to receive a signal from the rotor(602) and to identify the signature byte within the received signal(603). This process can repeat until STE 420 can identify the signaturebyte within a received signal (603, yes).

Upon identifying the signature byte, peak detector 427 can furtherdetermine a signal quality for the received signal and determine if thesignal quality is acceptable (605). As discussed above, thedetermination of signal quality may be based on one or morecharacteristics of the signal received by STE 420, or may be based oncharacteristics of the signal received at RTE 310 that are measured byRTE 310 and transmitted back to STE 420. In one example, RTE 310 maymeasure a recovered voltage and transmit back to STE 420 an indicationof the recovered voltage so that STE 420 can determine if the signalquality is at or above an acceptable level. If the signal quality is ofan acceptable level (605, yes), then STE 420 can send a confirmation oftuning to the rotor device and enter a normal mode of operation (606). Asignal may be deemed acceptable if, for example, peak detector 427detects a peak for the recovered voltage that is greater than athreshold value. In other implementations, peak comparator 428 maydetermine which recovered voltage of a set of recovered voltages resultsin the largest peak value, in which case a recovered voltage might bedeemed acceptable, for example, if it has the largest peak of the set.Micro-controller 430 can set variable capacitive element 424 to thecapacitance value that resulted in the acceptable signal quality. Theconfirmation of tuning sent by STE 420 can indicate to the rotor that adesired tuning has been achieved and that the rotor may enter a normalmode of operation.

If the signal quality of the signal containing the signature byte isdetermined not to be acceptable (605, no), then micro-controller 430 canadjust the capacitance of variable capacitive element 424, and STE 420can repeat the process of receiving a signal from the rotor (602),attempting to a identify a signature byte (603), adjusting capacitanceif a signature byte cannot be identified (604), and determining if asignal quality is acceptable (605) until an acceptable signal quality isfound (605, yes), and then STE 420 can send a confirmation of tuning andenter a normal mode of operation (606).

As mentioned, FIG. 6B is a flow diagram illustrating a rotor tuningtechnique consistent with the present disclosure. A rotor device, suchas rotor device 110 or 310, can be powered on and enter a tuning mode(621). As discussed above, powering on of RTE 310 may be achieved, forexample, by a user powering on a stator device, and the stator deviceinductively powering RTE 310. Upon being powered on, rotor device 310can enter a tuning mode in which micro-controller 321 causes a signaturebyte or a series of signature bytes to be transmitted via the LC circuitof box 318 (622). After sending the signature bytes, RTE 310 can wait aperiod of time to see if a confirmation of tuning is received from astator (623). If RTE 310 receives a confirmation of tuning (623, yes),then RTE 310 can enter a normal mode of operation (625). If RTE 310 doesnot receive a confirmation of tuning within a specified period of time(623, no), then micro-controller 321 can adjust the capacitance ofvariable capacitive element 317 (624), and RTE 310 can transmitadditional signature bytes (622). The process of adjusting variablecapacitive element (317), sending signature bytes (622), and waiting fora confirmation of tuning (623) can be repeated multiple times can berepeated until a confirmation of tuning is received, and RTE 310 entersa normal mode of operation (625).

The period of time RTE 310 waits to receive a confirmation of tuningmay, for example, be enough time for a stator device to execute severaliterations of the method described with regards to FIG. 6A. Thus, atorque measurement system may attempt to tune the system first by statortuning, and only if stator tuning is initially not successful does thesystem begin rotor tuning. Although not explicitly show in FIGS. 6A and6B, a torque measurement system, such as system 100, may be configuredto enter an error mode if neither stator tuning or rotor tuning resultin a desired overall system tuning.

Various examples have been described herein. These and other examplesare within the scope of the following claims.

The invention claimed is:
 1. A torque measurement system comprising: astator device configured to receive a signal from a rotor device, thestator device comprising: a first variable capacitive element; a firstmicro-controller configured to adjust a first capacitance value of thefirst variable capacitive element; and, a peak detector for detecting apeak value of the signal received from the rotor device, and wherein thefirst micro-controller adjusts the first capacitance value based atleast in part on the detected peak value.
 2. The torque measurementsystem of claim 1, further comprising: the rotor device, wherein therotor device is configured to transmit a signal to the stator device,the rotor device comprising: a second variable capacitive element; asecond micro-controller configured to adjust a second capacitance valueof the second variable capacitive element.
 3. The torque measurementsystem of claim 2, wherein the second micro-controller is configured toadjust the second capacitance value in response to not receiving aconfirmation of tuning message from the stator device within a period oftime.
 4. The torque measurement system of claim 2, wherein the secondmicro-controller is configured to enter a normal operating mode inresponse to receiving a confirmation of tuning message from the statordevice.
 5. The torque measurement system of claim 2, wherein the statordevice determines a value for the second capacitance value, and thesecond micro-controller adjusts the second capacitance based at least inpart on the determined value.
 6. The torque measurement system of claim1, wherein the first variable capacitive element comprises a firstswitch connected to a first capacitor, and wherein the firstmicro-controller adjusts the first capacitance value by opening andclosing the first switch.
 7. The torque measurement system of claim 6,wherein the first switch comprises a transistor-based switch.
 8. Thetorque measurement system of claim 6, wherein the first switch comprisesan electro-magnetic relay.
 9. The torque measurement system of claim 1,further comprising: a peak comparator for comparing a plurality of thedetected peak values of the signal received from the rotor device toidentify a preferred peak value, wherein the first micro-controlleradjusts the first variable capacitance value based on the preferred peakvalue.
 10. The torque measurement system of claim 1, wherein the signalfrom the rotor device includes data identifying a recovered voltage atthe rotor device, wherein the first micro-controller adjusts the firstcapacitance value based at least in part on the recovered voltage. 11.The torque measurement system of claim 1, wherein the stator devicefurther comprises: a signal processing module configured to identify asignature byte in the signal from the rotor device, and wherein thefirst micro-controller is configured to adjust the first capacitancevalue in response to not identifying the signature byte in the signalfrom the rotor device.
 12. The torque measurement system of claim 11,wherein the stator device is configured to transmit a confirmation oftuning to the rotor device in response to identifying the signature bytein the signal and the signal being of an acceptable quality.
 13. Thetorque measurement system of claim 11, wherein the firstmicro-controller is configured to adjust the first capacitance value inresponse to the stator identifying the signature byte and the signal notbeing of an acceptable quality.
 14. A torque measurement systemcomprising: a rotor device configured to transmit a signal to a statordevice, the rotor device comprising: a variable capacitive element; amicro-controller configured to adjust a capacitance value of thevariable capacitive element; and, a peak detector for detecting a peakvalue of the signal received from the rotor device, and wherein thefirst micro-controller adjusts the first capacitance value based atleast in part on the detected peak value.
 15. The torque measurementsystem of claim 14, wherein the variable capacitive element comprises aswitch connected to a capacitor, and wherein the micro-controller isconfigured to adjust the capacitance value by opening and closing thefirst switch.
 16. The torque measurement system of claim 15, wherein theswitch comprises a transistor-based switch.
 17. The torque measurementsystem of claim 15, wherein the switch comprises an electro-magneticrelay.
 18. The torque measurement system of claim 14, wherein themicro-controller is configured to adjust the capacitance value inresponse to not receiving a confirmation of tuning message from thestator device within a period of time.
 19. The torque measurement systemof claim 14, wherein the micro-controller is configured to enter anormal operating mode in response to receiving a confirmation of tuningmessage from the stator device.
 20. The torque measurement system ofclaim 14, further comprising: a peak comparator for comparing aplurality of the detected peak values of the signal received from therotor device to identify a preferred peak value, wherein the firstmicro-controller adjusts the first variable capacitance value based onthe preferred peak value.